Abstract 20969: Higher Implant Norepinephrine Transporter Levels in the Myocardium are Associated with Myocardial Recovery during Left Ventricular Assist Device Support
Cardiac norepinephrine transporter (NET) uptake sites are markedly impaired in heart failure (HF) patients resulting in intracardiac abundance of norepinephrine (NE) which in turn overactivates the cardiac sympathetic system, a hallmark in the progression of HF. Left ventricular assist devices (LVADs) improve NET activity and reduce NE levels. The bearing of NET, however, in determining which LVAD patients favourably recover has not been studied. The aims of this study were to quantify NET using immunostaining in the myocardium of HF patients acquired during LVAD implantation and to correlate the NET expression with subsequent recovery.
Methods: Left ventricular (LV) apical cores were obtained from patients with end stage HF (cardiac index 1.49±0.33 l/min/m2) at the time of HeartMateII implantation. Tissue was snap frozen at -80°C. After fixation, sections were incubated overnight at 4°C with primary rabbit NET antibody (ATLAS Antibodies) at 1:100 concentrations. Secondary antibody was applied and avidin biotin peroxidase complex was used for labelling. Perioxidase was then developed using nickel enhanced diaminobenzidine to produce different colorimetric layers. Images were captured digitally and analysed by two independent observers using analySIS software (Olympus version 5.0). NET immunoreactivity was calculated as the average percentage area covered from randomly selected 5 different regions for each patient.
Results: 16 patients (14 males) were studied. 11 had recovered and had their LVAD explanted. The percentage NET immunoreactive nerve fibers per area were significantly higher in the recovered patients at the time of implantation (1.04±0.30% vs 0.65±0.43%, P=0.05). There was a moderate correlation between NET immunoreactive nerve fibers and myocardial recovery (R=0.512, P=0.035). Intraclass correlation coefficient between both observers revealed a moderate reliability of 45.8% (R= 0.464, P=0.028).
Conclusion: Patients recovered with LVAD support had a higher percentage of NET immunoreactive nerve fibers per total area in the LV apex at the time of implantation as compared to non recovered patients. Immunostaining evaluation of NET immunoreactive nerve fibers at implantation correlated with subsequent myocardial recovery.
- © 2010 by American Heart Association, Inc.